I need to change callback methods to promise function

PluginRes.prototype.startup = function(successCallback, errorCallback) {
if (errorCallback == null) {
errorCallback = function() {}
}

if (typeof errorCallback != "function") {
console.log(" failure parameter not a function");
return
}

if (typeof successCallback != "function") {
console.log(" success callback parameter must be a function");
return
}

exec(successCallback, errorCallback, "PluginRes", "startup", []);
};